The invention relates to amplifiers and more particularly to low noise amplifiers.
It is well known that in small signal applications, noise generated by or in, and contributed by an amplifier in a circuit for amplifying the small signal could overpower the signal.
It is an object of the present invention to provide an amplifier arrangement and method of amplifying a signal with which the applicant believes the aforementioned problems may at least be alleviated.
According to the invention there is provided an amplifier arrangement comprising:
an input node;
an output node;
a plurality of amplifiers connected in respective parallel paths extending between the input node and the output node;
the input node dividing an input signal into signal parts and feeding the signal parts along respective paths to the output node; and
the paths having equal propagation delays for the signal parts, to provide at the output node an output signal comprising a coherent summation of the signal parts.
The amplifier arrangement may comprise a first transmission medium having one end and an opposite end and a second transmission medium having one end and an opposite end, the input node may be provided towards the one end of the first transmission medium, the output node may be provided towards the opposite end of the second transmission medium and the parallel paths preferably extend between the first transmission medium and the second transmission medium.
A spacing between one of said parallel paths and an adjacent parallel path on the first transmission medium is preferably equal to a spacing between the one path and the adjacent path on the second transmission medium.
Termination means may be provided at the opposite end of the first transmission medium and at the one end of the second transmission means.
The amplifier arrangement may be adapted for amplifying a pulse having a pulse width and the spacing is preferably larger than a distance through which the pulse would travel through the medium in a time equal to the pulse width.
One of the first transmission medium and the second transmission medium may comprise a transmission line.
In some embodiments each of the first transmission medium and the second transmission medium comprises a coaxial cable.
In other embodiments each of the first transmission medium and the second transmission medium comprises a strip line.
In yet another embodiment the first transmission medium may comprise a transmission line and the second transmission medium may comprise a two dimensional conductive layer.
In still another embodiment the second transmission medium may comprise a three-dimensional cavity. The cavity may comprise signal absorbent means.
Also included within the scope of the present invention is a method of amplifying a signal comprising the steps of:
at an input node, dividing the signal into signal parts propagating along respective paths to an output node;
amplifying the signal parts in the paths by amplifying means in the paths;
causing a propagating delay in each of the paths to be the same;
at the output node, coherently summing the amplified signal parts to provide an output signal; and
incoherently summing noise added by the amplifiers.
The output signal is preferably caused to propagate in predominantly a first direction towards an output, noise is preferably caused to propagate in another direction as well, and the noise propagating in the other direction is absorbed.